JP2906847B2 - High frequency amplifier circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency amplifier circuit used in, for example, a digital portable telephone.

[0002] Mobile communication devices such as digital portable telephones include:
There is a trend toward smaller size and lower power consumption. For this reason, it is necessary to reduce the circuit scale of the amplifier circuit so that the circuit is suitable for IC.

[0003]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional example. Usually, in a high-frequency amplifier circuit used for a digital cellular phone, etc.,
Radio frequency amplifier portion 12 as shown in figure transceiver antenna with ANT ₂
Amplifies the signals received from the addition to the high frequency switch 13, also amplifies the signal RF amplifier portion 11 is received from the reception antenna ANT ₁ is added to the high-frequency switch 13. Therefore, the high-frequency switch selects the output of one of the high-frequency amplification sections and sends it to the outside in response to a control signal from the outside. Reference numeral 15 denotes a transmission unit, and 14 denotes a transmission / reception splitter.

Here, the high-frequency switch is, for example, GaAs
An MMIC (monolithic microwave IC) switch using FETs is used to electrically disconnect the amplifying part on the unselected side. The effect of the part is eliminated to prevent deterioration of the characteristics.

[0005]

Here, when an IC of a high frequency amplifier circuit is considered, a silicon bipolar transistor is used for a high frequency amplifier and the like in terms of cost and mass productivity, but a high frequency switch is a silicon bipolar transistor. Since it is technically difficult to construct with transistors, another IC (
For example, two types of ICs are required.

For this reason, the above-described high-frequency amplifier circuit using a high-frequency switch is not suitable for integration into an IC, and has a problem that it is difficult to reduce the circuit scale. An object of the present invention is to provide a circuit suitable for IC integration by reducing the circuit scale.

[0007]

FIG. 1 is a block diagram showing the principle of the first and second embodiments of the present invention. In the figure, reference numeral 2a denotes an emitter of a first transistor grounded by a resistor, a collector grounded by a capacitor, and connected to an emitter of a second transistor. The collector of the second transistor is connected via a resistor and a capacitor. A DC voltage is supplied to a collector of the third transistor, a high-frequency signal is input to a base of the second transistor, and an emitter of the third transistor is connected to the emitter and the base of the third transistor. This is the first high-frequency amplification section that outputs.

Reference numeral 3a denotes a first bias voltage supply section for generating a predetermined bias voltage using the applied reference voltage and supplying the generated bias voltage to the bases of the first to third transistors, and 2b denotes a first high-frequency amplifier. A second high-frequency amplifier having the same configuration and function as the first portion, 3b has the same configuration as the first bias voltage supply portion, a second bias voltage supply portion having the same function, and 4 corresponds to the state of the applied switching signal. And a switching section for cutting off the supply of one of the DC voltages supplied to the first and second high-frequency amplification sections.

According to a first aspect of the present invention, the emitters of the third transistors in the first and second high frequency amplifying portions are directly connected to each other to extract a high frequency signal through a DC blocking capacitor and to set a reference voltage. The configuration is such that the voltage is applied to both the first and second bias voltage supply portions.

According to a second aspect of the present invention, a reference voltage is commonly applied to the first and second bias voltage supply portions via first and second resistors.

[0011]

According to the first aspect of the present invention, when the DC voltage (V _CC ) of the other high-frequency amplification section is turned off by the switching section by directly connecting the output terminals of the two high-frequency amplification sections in a DC manner, The DC voltage appearing at the output terminal of the high-frequency amplifier also appears at the output terminal of the other high-frequency amplifier, and the output impedance of this amplifier is made high (described later in detail). For this reason, even if the high-frequency switch is not provided, one high-frequency amplifier is hardly affected by the other high-frequency amplifier.

Since the output terminals are directly connected, a leakage current of about several 100 μA flows through the inactive high-frequency amplifier. According to the second aspect of the present invention, in order to further reduce the leakage current, a reference voltage is applied to both the first and second bias voltage supply portions via, for example, a resistor of several kilohms to several tens of kilohms. As a result, the reference voltage applied to the other high-frequency amplifier decreases, so that the leakage current decreases and the power consumption of this amplifier decreases.

That is, it is possible to provide a circuit suitable for IC by reducing the circuit scale.

[0014]

FIG. 2 is a block diagram of the first and second embodiments of the present invention, FIG. 3 is an explanatory diagram of the output impedance of the amplifier, FIG. 4 is a gain characteristic diagram of the amplifier, and FIG. It is a frequency conversion part block diagram utilized.

Here, the switches SW ₁ and SW ₂ are constituent parts of the switching part. The same reference numerals indicate the same objects throughout the drawings. Hereinafter, the states of the switches SW ₁ and SW ₂ are indicated by solid lines.
(The high-frequency amplification section 2a is in the operating state and the high-frequency amplification section 2b is in the non-operation state), and the resistors R _7a and R _7b are set to 0, and FIG.
The operation of FIG. 2 will be described with reference to FIG. Note that a control signal for driving the switch is externally applied.

[0016] First, the bias voltage supply section 3a includes a transistor Q _21a (hereinafter, abbreviated as Q _21a), is intended for supplying a base voltage necessary based Q _22a, Q _23a, 4
Transistors Q _31a , Q _32a , Q _33a , Q _34a
Since the connection is made by stacking in columns, the voltage drops below the voltage _Vcc every time the transistor passes through each stage.

For example, if V _cc = + 5V, the V of Q _34a
be emitter voltage of because it is about 0.8V Q _34a becomes 4.2V. When the base voltage of Q _33a supplied from the reference voltage generating portion 4, for example, + 2.8V, the emitter voltage of Q _33a is + 2V, the emitter voltage of Q _32a is + 1.2V, and the these voltages Q _23a , Q _22a , applied to the base of Q _21a . Note that V _be of Q _{33a and} Q _32a is set to about 0.8 V similarly to the above.

Now, when the bias voltage is applied to Q
The _22a-based, the high frequency signal is applied through a capacitor C _11, the high-frequency signals the collector of Q _22a, applied to the base of Q _23a via the capacitor C _5. So Q _23a
High-frequency signal is further amplified by the amplified by the emitter in is output via the capacitor C _13, the terminal OUT.

At this time, the DC current flowing from the reference voltage generating part 5 to the high frequency amplifying part Q _33a in the operating state is several μm.
A However, the high frequency amplifier portion 2b in a non-operating state, Q _23b from V _cc during operation, Q _22b, a current which has been flowing through the Q _21B, to several 10μA from several μA to flow from the reference voltage source increases I do.

As a result, a voltage is generated at Q _21b ,
Since there is a potential difference between the emitter voltage of the emitter voltage = Q _23b of _23a, Q _22b, a fraction of the current flows in the normal through the Q _21b, the output impedance of the high frequency amplifier portion 2b increases.

FIG. 3 shows the output impedance (A1-A1 ') when one high-frequency amplifier is activated, the output impedance (A2-A2') when it is inactive, and the inactive state. , the output impedance when applying a same emitter voltage and operating state to the emitter of Q _23b (B1-B1')
Is shown on the Smith diagram.

Here, points A1, A2, and B1 are points at a frequency of 50 MHz, points A1 ', A2', and B1 'are points at a frequency of 5 GHz, and (A2
-A2 ') is the case of the conventional example, and (B1-B1') is the case of the present invention.

As shown in FIG. 3, (A1-A1 ') and (A2-A2
(A) has almost the same output impedance in the high frequency region, whereas (A1-A1 ') and (B1-B1') have output impedances higher in the latter state than in the former state. I have.

FIG. 4 shows the frequency characteristics when the voltage application condition of one high-frequency amplifier is the same as that of FIG. 3. C1 is the operating state (in the case of a single unit), and D1 is the non-operating state of the operating high-frequency amplifier. When the high-frequency amplification part in the state is connected (conventional example), E1
Shows the case where the non-operating high-frequency amplifier is connected to the operating high-frequency amplifier (in the case of the present invention).

As shown in FIG. 4, in the case of the present invention, it is shown that even if the non-operating high frequency amplifying part is connected, it is hardly affected. Next, the operation of FIG. 5 will be described. In FIG. 5, 2a, 2b, 3a, 3b, and 4 are the same as those in FIG.

[0026] First, the reference voltage generating portion 5 by using the DC voltage V generates a predetermined reference voltage, the resistor R _7a, is applied via the R _7b Baiai voltage supply part 3a, to 3b. The bias voltage supply sections 32a and 32b generate a predetermined bias voltage and supply the generated bias voltage to the corresponding high-frequency amplification sections 2a and 2b. As described above, for example, it is assumed that the high-frequency amplification section 2b is in an inactive state.

The two series of high-frequency signals are added to the high-frequency amplification sections 2a and 2b via the band-pass filters 51a and 51b. The high-frequency signals amplified only by the high-frequency amplification section 2a are mixed via the band-pass filter 54 with the mixer. Send to 53. Mixer
Since the bias voltage from the mixer bias voltage supply section 52 is applied to 53 and a local signal is also applied via a band-pass filter, the high-frequency signal is frequency-converted into an intermediate frequency band signal and is not shown. It is sent to the subsequent stage.

That is, according to the first and second aspects of the present invention, without using a high frequency switch, without deteriorating the characteristics,
Since the outputs of the two high-frequency amplifiers can be connected, it is possible to provide a circuit suitable for IC integration, which can greatly contribute to a reduction in the number of components and cost.

[0029]

As described in detail above, according to the present invention, there is an effect that the circuit scale can be reduced to provide a circuit suitable for IC.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of first and second embodiments of the present invention.

FIG. 2 is a configuration diagram of the first and second embodiments of the present invention.

FIG. 3 is an explanatory diagram of an output impedance of an amplifier.

FIG. 4 is a gain characteristic diagram of the amplifier.

FIG. 5 is a configuration diagram of a frequency conversion unit using the second invention.

FIG. 6 is a configuration diagram of a conventional example.

[Explanation of symbols]

2a first high-frequency amplification part 2b second high-frequency amplification part 3a first bias voltage supply part 3b second bias voltage supply part 4 switching part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H03F 3/189-3/195 H03F 3/72 H03K 17/00 H04B 1/06-1/58

Claims (2)

(57) [Claims] 1. An emitter of a first transistor is grounded by a resistor, a collector is grounded by a capacitor, and
The collector of the second transistor is connected to the emitter and the base of the third transistor via a resistor and a capacitor, and a DC voltage is supplied to the collector of the third transistor. A first high-frequency amplifier (2a) configured to input a high-frequency signal to the base of the second transistor and to output the high-frequency signal from the emitter of the third transistor; And a first bias voltage supply section (3a) for generating a bias voltage and supplying the bias voltage to the bases of the first to third transistors, wherein the first high-frequency amplification section and the first bias The second high-frequency amplification part (2b) and the second bias voltage supply part (3b) having the same configuration and the same function as the voltage supply part, and corresponding to the state of the applied switching signal, A switching section (4) for interrupting the supply of one of the DC voltages supplied to the first and second high-frequency amplification sections; and a third section in the first and second high-frequency amplification sections. The transistors are directly connected to each other, a high-frequency signal is taken out via a DC blocking capacitor, and the reference voltage is applied to both the first and second bias voltage supply portions. High-frequency amplifier circuit. 2. The high-frequency amplifier circuit according to claim 1, wherein said reference voltage is applied to both said first and second bias voltage supply portions via first and second resistors.